Rotors for electric machines, especially for transversal flow machines, are known in a number of variants with respect to configuration and/or assembly, for example, from the following documents:
1. DE 92 00 116 U1 PA1 2. EP 0 642 204 A1 PA1 1) a specified spacing a.sub.1 is provided between the outside diameter of the magnetic arrangement and the protrusion on the collector and soft iron element or PA1 2) in magnet arrangements with different dimensions in the peripheral direction over PA1 1) recesses of larger dimension or PA1 2) omission of an outer protrusion, relative to the face forming the stop. PA1 1) at least one annular pole structure extending on one face of the support disk in the axial direction away from the central support disk or PA1 2) one pole structure on both sides of the faces of the support disk in provided.
The rotor of a transversal flow machine then comprises one or more axially adjacent, concentric rings (active rings) separated from each other by rings made of plastic or another electrically nonconducting material lying in between and/or a rotor disk, in which so-called collector and soft iron elements, which can usually be made from axially layered magnetic steel sheet, and magnets are arranged in alternation on the periphery. These concentric rings are also referred to as the pole structure.
The rotor design described in DE 92 00 116 U1 has collector and soft iron elements that are provided on their sides facing the magnet arrangements with U-shaped recesses in the peripheral direction, into which the magnets are inserted. Two protrusions are formed by these recesses, which partially enclose the magnet arrangement. The width of the recess or its dimension in the radial direction is then slightly greater than the surface length l, i.e., the dimension of the magnetic arrangement in the radial direction. A shape-mated anchoring between each magnet arrangement and the two adjacent collector and soft iron elements is achieved by this expedient. However, a glue joint between the magnet arrangement and the collector and soft iron elements is preferably also retained. To avoid a conducting connection between the collector and soft iron elements and the magnet, which leads to severe heating of the rotor and can also adversely affect the magnetic properties of the magnet arrangement, an insulation layer is provided in the region of the U-shaped recesses on the contact surfaces between the collector and the soft iron element and the magnet arrangement.
To achieve small rotor arrangements in which a small pole division is desired, EP 0 642 204 A1 discloses a variant in which the rotor has a rotor disk that can be fastened to the rotor axis in the axial direction, on which the polarized magnets and the magnetizable collector and soft iron elements are attached in a concentric ring arrangement, in which attachment occurs with fastening elements that pass through the polarized magnets, which are designed in two parts, at least in the arrangement region of the fastening element, and are attached to the rotor disk or to an insulation element connected to the rotor disk in the axial direction. Here again the magnet arrangements are connected in shape-mated fashion and/or bonded to the adjacent collector and soft iron elements in the peripheral direction. A shortcoming of the use of these elements which additionally secure against peel stress, is mostly the fact that these require a significant increase in rotor weight and rotor volume and thus an increase in active volume subject to loss. The holes for the threaded inserts and screw holes to be provided for assembly of the securing elements require high manufacturing and machining costs. When the securing or fastening elements are arranged through the active rings, either the magnets must be provided in divided form, i.e., in double numbers, or when such elements are made or arranged in the region of the collector and soft iron elements, these are subject to high machining and assembly costs. In a rotor corresponding to the variant described in EP 0 642 204 A1, the centrifugal forces that occur at high speeds can no longer be economically managed by joining with external force and bonding (especially screwing and gluing).
A shortcoming of such arrangements consists of the fact that, when only shape-mated connections are provided between the magnets of the magnet arrangement and the adjacent collector and soft iron elements in the peripheral direction, the magnet arrangements are forced against the radially outer protrusions owing to the centrifugal forces occurring during operation of the rotor even with simultaneous position fixation in the radial direction of the collector and soft iron elements relative to the adjacent elements in the axial direction, like the end ring, intermediate ring and support disk, and make possible an electrically conducting connection between the collector and soft iron elements and the magnet arrangement, which can lead to undesired high heating of the rotor. The magnets are also loaded by heat conduction and their magnetic properties are adversely affected, which can lead to complete demagnetization of the magnets. In variants with an insulation layer provided on the collector and soft iron elements, there is a hazard that the insulation layer in this region is damaged on the collector and soft iron element and a conducting connection is produced between the collector and soft iron element and magnet arrangement owing to the centrifugal forces that act on the magnet arrangements and force the magnet arrangements in the radial direction against the protrusions on the collector and soft iron element that form a stop in the radial direction and are arranged in the region of the outside diameter of the collector and soft iron element, which leads to the already mentioned shortcomings.
The underlying task of the invention is therefore to further modify a rotor of an electric machine so that the mentioned shortcomings are avoided. In particular, the additional losses that result in severe heating of the rotor and adversely affect the magnetic properties of the magnets during failure of the insulation layer are to be avoided with retained rotor strength in rotors of the type mentioned at the outset with shape-mated connection between the collector and soft iron elements and the magnet arrangement. The design and manufacturing costs are to be kept as low as possible.